fiat

American  

[fee-aht, -at, fahy-uht, -at] / ˈfi ɑt, -æt, ˈfaɪ ət, -æt /

noun

1. an authoritative decree, sanction, or order.

   a royal fiat.

   Synonyms:

   ukase, diktat, mandate, ruling, directive, authorization

2. a fixed form of words containing the word fiat, by which a person in authority gives sanction, or authorization.

3. an arbitrary decree or pronouncement, especially by a person or group of persons having absolute authority to enforce it.

   The king ruled by fiat.

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fiat British  

/ ˈfaɪət, -æt /

noun

1. official sanction; authoritative permission

2. an arbitrary order or decree

3. literary any command, decision, or act of will that brings something about

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Etymology

Origin of fiat

First recorded in 1625–35; from Latin: “let it be done,” 3rd-person singular present subjunctive of fierī “to become”

Example Sentences

These purchase decisions are being made by fiat, as federally owned property is often exempt from local permitting and zoning rules.

From Slate • Mar. 12, 2026

Rock leads Binance’s so-called fiat business, which turns crypto into regular money.

From The Wall Street Journal • Feb. 23, 2026

Wars are financed by borrowing and printing money which devalues debt and fiat currency.

From MarketWatch • Feb. 16, 2026

Generally, the fiat currency with less indebtedness problems, the stronger it has been—like the Swiss franc.

From Barron's • Feb. 6, 2026

The huge stableboy put both hands fiat on the door, pushed, and grunted.

From "A Clash of Kings" by George R.R. Martin